MEDIAN NERVE PALSY

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MEDIAN NERVE PALSY

Q. 1

If median nerve is injured at the wrist then loss of function of all of the following will take place except?

 A

Lumbrical muscles to the Index finger.
 B

Lumbrical muscles to the middle finger.
 C

Muscles of the thenar eminence
 D

Adductor pollicis
Q. 1

If median nerve is injured at the wrist then loss of function of all of the following will take place except?

 A

Lumbrical muscles to the Index finger.
 B

Lumbrical muscles to the middle finger.
 C

Muscles of the thenar eminence
 D

Adductor pollicis
Ans. D
Explanation:

Motor nerve supply of Median nerve in the hand:

Thenar muscles which include

  1. Flexor pollicis brevis
  2. Opponens pollicis
  3. Abductor pollicis
Q. 2  

TRUE/FALSE statements about carpal tunnel syndrome are:

 

 

 

1. Occurs in pregnancy

 

2. Affects medial three and half fingers

 

3. Associated with hypothyroidism

 

4. Froment sign positive

5. Median nerve involvement is present

 A 1,2,3 true & 4,5 false
 B

1,3,5 true & 2,4 false
 C

1,2,3,4 true & 5 false
 D

1,2,3,5 true & 4 false
Ans. B
Explanation:

Carpal tunnel syndrome is caused by the compression of the median nerve at wrist and is most common type of nerve entrapment syndrome.

 This is usually due to excessive use of the hands and occupational exposure to repeated trauma.

Infiltration of the transverse carpal ligament with amyloid (as occur in multiple myeloma) or thickening of connective tissue in rheumatoid arthritis, acromegaly, amyloidosis, mucopolysaccharidosis and hypothyroidism are less common cause of the syndrome.

It is not uncommon for the condition to make its appearance during pregnancy.

The syndrome is essentially a sensory one; the loss or impairment of superficial sensations affect the palmar aspect of the thumb. Index and middle fingers (especially the index finger) and may or may not split the ring finger. So the lateral three and half fingers are involved (not medial 3 1/2 fingers). The paresthesia are characteristically worsen during night.

 

 

 

Froment sign is seen in ulnar nerve injuries not in median nerve injuries.

Ref: Apley’s 8/e, Page 247-48; Harrison 17/e, Page 2153-54, 2231, 47; Maheshwari 3/e, Page 56.

 

Q. 3

Which of the following carpal bone fracture causes median nerve involvement?

 A

Scaphoid
 B

Lunate
 C

Trapezium
 D

Trapezoid
Ans. A
Explanation:

In all age groups, the fracture may be complicated by injury to the median nerve, injury to the sensory branch of the radial nerve, fracture of the scaphoid, and/or dislocation of the lunate.

Bones in the proximal row are the most frequently fractured. Scaphoid fracture is by far the most common carpal bone fracture so the injury is mostly seen in scaphoid bone.

 

 

Ref: Rockwood & Green’s fracture in Adults 6/e, Page 864-82.

 

Q. 4

TRUE/FALSE about peripheral nerve injuries in upper limb are:

1. Radial nerve injury cause anaesthesia over anatomical snuff box
2. Medial nerve cause wrist drop
3. Ulnar nerve causes claw hand
4. Index finger anesthesia is caused by median nerve injury
5. Thumb anesthesia is caused by ulnar nerve injury
 

 A

1,2,3 true & 4,5 false
 B

2,3,4 true & 1,5 false
 C

1,3,4 true & 2,5 false
 D

1,2 false & 3,4,5 true
Ans. C
Explanation:

Options 1 (true)
The cutaneous branch of the radial nerve supply the skin over anatomical snuff box, as such radial nerve injury causes anaesthesia over anatomical snuff box.

Option 2 (false)
Paralysis of the extensor muscles of the forearm produces wrist drop. This is usually due to the radial nerve above the level of origin of posterior interosseous nerve, e.g. in axilla and arm.
Option 3 (true)
Claw hand can be produced by many lesions, including lesions of ulnar nerve, a combined lesions of ulnar nerve and median nerves, klumpke’s paralysis, lesion of the medial cord of brachial plexus.
Option 4 (true) and 5 (false)
Lateral three and half digits (palmar aspect of middle and distal phalanges) are supplied by median nerve.
 
Lateral half of dorsum of hand including proximal phalanges of lateral two and half digits is supplied by radial nerve.
Q. 5 If median nerve is injured at the wrist, then loss of function of all of the following muscles will take place, EXCEPT?

 A

Lumbrical muscles to the Index finger
 B

Lumbrical muscles to the middle finger
 C

Muscles of the thenar eminence
 D

Adductor pollicis
Ans. D
Explanation:

Median nerve (C6–T1): Provides most of the innervation to the anterior forearm, excluding one and one half muscles, the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus muscle, which are innervated by the ulnar nerve. The median nerve continues into the hand to innervate the thenar eminence and lumbricals 1 and 2. It provides cutaneous innervation to the medial palmar side of the hand and the palmar surface of digits 1 through 3 and half of digit 4.

Adductor pollicis is supplied by ulnar nerve.

Q. 6

If median nerve is injured at the wrist then loss of function of all of the following will take place except:

 A

Lumbrical muscles to the Index finger.
 B

Lumbrical muscles to the middle finger
 C

Muscles of the thenar eminence
 D

Adductor pollicis
Ans. D
Explanation:

D i.e. Adductor pollicis

Q. 7

Median nerve injury at wrist, is commonly tested by:

 A

Contraction of abductor pollicis brevis
 B

Contraction of flexor pollicis brevis
 C

Loss of sensation on palm
 D

Loss of sensation on ring finger
Ans. A
Explanation:

Injury or compression of median nerve at wrist (eg carpel tunnel syndrome) can be tested by

1.      Pen test for loss of action of Abductor pollicis brevis

2.      Ape thumb deformity Q (adducted posture of thumb)

3.      Loss of opposition & abduction of thumb Q (d/ t wasting of thenar muscles)

4.      Sensory loss – lateral 31/2 of digits & 2/3 palm (autonomous zone is tip of index & tniddle finger)

Abductor pollicis longus is supplied by posterior interosseous nerve (br. of radial nerve)Q; so abduction of thumb is not completely lost.

Q. 8

Which carpal bone fracture causes median nerve involvement?

 A Scaphoid
 B

Lunate
 C

Trapezium
 D

Trapezoid
Ans. B
Explanation:

B i.e. Lunate

Lunate dislocation is an uncommon injury occurring in young adults due to high-energy trauma. Median nerve injury is common if the lunate dislocates volarly into the carpal tunnel

Q. 9

Median nerve lesion at the wrist causes all of the following.except ‑

 A

Thenar atrophy
 B

Weakness of Adductor pollicis
 C

Weaknes of 1st and 2nd lumbricals
 D

Weakness of Flexor pollicis brevis
Ans. B
Explanation:

Ans. is ‘b’ i.e., Weakness of Adductor pollicis

Adductor pollicis is supplied by ulnar nerve.


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